son to suppose that the character of the
excentricity would suddenly change beyond the three million years.

It follows, therefore, that if periods of high excentricity, like that
which appears to have been synchronous with our last glacial epoch and is
generally admitted to have been one of its efficient causes, always
produced glacial epochs (with or without alternating warm periods), then
the whole of the Tertiary deposits in the north temperate and Arctic zones
should exhibit frequent alternations of boulder and rock-bearing beds, or
coarse rock-strewn gravels analogous to our existing glacial drift, and
with some corresponding change of organic remains. Let us then see what
evidence can be adduced of the existence of such deposits, and whether it
is adequate to support the {67} theory of repeated glacial epochs during
the Tertiary period.

_Evidences of Ice-action during the Tertiary Period._--The Tertiary fossils
both of Europe and North America indicate throughout warm or temperate
climates, except those of the more recent Pliocene deposits which merge
into the earlier glacial beds. The Miocene deposits of Central and Southern
Europe, for example, contain marine shells of some genera now only found
farther south, while the fossil plants often resemble those of Madeira and
the southern states of North America. Large reptiles, too, abounded, and
man-like apes lived in the south of France and in Germany. Yet in Northern
Italy, near Turin, there are beds of sandstone and conglomerate full of
characteristic Miocene shells, but containing in an intercalated deposit
angular blocks of serpentine and greenstone often of enormous size, one
being fourteen feet long, and another twenty-six feet. Some of the blocks
were observed by Sir Charles Lyell to be faintly striated and partly
polished on one side, and they are scattered through the beds for a
thickness of nearly 150 feet. It is interesting that the particular bed in
which the blocks occur yields no organic remains, though these are
plentiful both in the underlying and overlying beds, as if the cold of the
icebergs, combined with the turbidity produced by the glacial mud, had
driven away the organisms adapted to live only in a comparatively warm sea.
Rock similar in kind to these erratics occurs about twenty miles distant in
the Alps.

The Eocene period is even more characteristically tropical in its flora and
fauna, since palms and Cycadaceae, turtles, snakes, and cro